Historical perspectives OfRadiology
Dr Deebika Vinothprabu
Dr Deebika vinothprabu
History of radiology
1895 – Wilhelm Conrad Roentgen detects x rays & take first x ray
1896 – Antoine Henri Becquerel discovers radioactivity
1896 – Thomas Alva Edison invents first commercially available fluoroscope
1913 – Albert Salmon – mammography
1927 – Egas Moniz – cerebral angiography
1950 – David e.kuhl invents PET
• 1953 – Sven Ivar Seldinger – seldinger technique
• 1957 – Ian Donald – ultrasound
• 1964 – Charles Dotter – image guided intervention
• 1972 – Godfrey Hounsfield & Allan m.Conmarck – CT
• 1977 – Raymond Vahan Damadian – mri scanner
History of X rays
Discovery of x rays was the beginning of revolutionary change German physicist WILHELM CONRAD RONTGEN discovers x rays – 1895
Nobel prize in physics in 1901
In 2004, international union of pure and applied chemistry named element 111 as ROENTGENIUM(radio active element)
• In early november he was investigating external effects of various vacuum tubes.
• While doing experiments with vacuum tubes,he added aluminium window to permit cathode rays to exit & a cardboard covering added to protect aluminium from damage by electrostatic field that is necessary to produce cathode rays
• Roentgen observed invisible rays caused fluorescent effect on carboard screen painted with barium platinocyanide
• He investigated various properties of rays which he called ‘X RAYS’
• He took the very first picture using x rays of his wife Anna berthas’s hand
X RAYS part of electromagnetic spectrum
Wide range of Wavelength
Deeply penetrating,highly destructive shorter wavelength – HARD X RAYS
Longer wavelength,lesser penetrating power – SOFT X RAYS
Soft xrays – used in medical & dental diagnosis
Ionising radiation
Carries high energy & deposits a part of it within the body it passes
Cause biological effects
X ray tubes Crookes tube
-invented by william crookes
-first used x ray tubes -used untill 1920
-generate electrons by ionization of residual air in the tube
-used an aluminium cathode, platinum anode
-unreliable as residual air in tube absorbed by walls
Coolidge tube
• Improved by william coolidge 1913• Most widely used• Electrons produced by thermionic effect• Tungsten filament(cathode) heated by electric current• High voltage potential between cathode & anode• Electrons accelerated hit anode
X-Ray tube
Filament
Rotor
Vacuum envelopeAnode
Cathode
X rays produced due to sudden deceleration of fast moving electrons when they collide & interact with target anode99% electron energy converted to heat and 1% into x ray productionCathode(tungsten filament) is the negative terminal of x ray tubeWhen current is flowing through it filament gets heated and start emitting electrons by process called thermionic emissionHigh voltage applied between cathode and anode
Anode(tungsten disc) is the positive terminal.fast moving electron interact with anode in 3 ways1)Interaction with K-shell electron – charecteristic x rays2)Interaction with nucleus – bremsstrahlung radiation3)Interaction with outer shell electron – line spectrum
In early 1896 in the wave of excitement following Roentgen’s discovery of x rays, Antoine Henri Becquerel ,french physicist thought that phosphorescent materials such as Uranium salts emit penetrating x ray like radiation when illuminated by sunlight
Discoverer of radioactivity1903 – received nobel prize in physics along with Marie Curie & Pierre Curie
Fluoroscopy
• First crude fluoroscope created within months after x ray discovery
• Use of x rays to produce a moving image of internal structure of patient
• Fluoroscopy uses continuous x ray beam that is passed over area of interest
• Frequently used to evaluate GI tract,kidney function etc
Computerised radiography
• Similar to conventional radiography except that in place of the flim to create the image,an imaging plate made of photostimulable phosphor used
• Imaging plate is housed in a special cassette and placed under the object and xray exposure made
• Imaging plate is run through a special laser scanner that reads the image
Digital x ray
• X ray sensors(digital image capture device)are used instead of traditional photographic film
• Time efficiency
• Ability to digitally transfer & enhances image
• Less radiation
• Immediate image preview & availability
• Eliminates costly film processing
Mammogram
1949 – Raul Leborgne,radiologists introduced compression technique
Late 50’s –Robert L.Egan,radiologists introduces a new technique using fine-grain intensifying screen & industrial film for clearer images
MID 60’s – gain acceptance as screening tool
german surgeon Albert Salmon attempts to visualize cancer of breast through radiograph1913
1949
Late 50’s
MID 60’s
– modern day film mammogram invented 1969
1993
2000
2011
– mammogram recommended as screening tool by American Cancer Society
– FDA approves first digital mammography system
– FDA approves Hologic’s 3D mammography technology(breast tomosynthesis),proven clinically superior to digital mammography
Ultrasonogram
• Ian Donald – first diagnostic application of usg – 1956,one dimentional A mod (amplitude mode)
• 1963 – B mode(brightness mode)two dimentional devices constructed
• Turning point in application of ultrasound in medicine
• In mid seventies (kossoff garrett)introduction of real time ultrasound scanner
• Decade later,doppler effect enabled visualization of blood circulation
• Ultrasound refers to sound waves with frequency too high for humans to hear
• Images made by sending a pulse of ultrasound into tissue using ultrasound transducer
• Sound reflected fron parts of tissue recorded as image
Modes
A-MODE : -simplest type -single transducer scans a line through the body with echoes plotted on screens function of depth -therapeutic ultrasound for tumor or calculus for pinpoint focus of destructive wave energy
B MODE : Linear array of transducers scan a plane that viewed as two – dimentional image on screen
M – MODE : M for motion rapid sequence of B mode scans images follow each other in sequences ,enable see & measure range of motion commonly used to measure cardiac dimensions & ejection fraction
DOPPLER MODE : In measuring & visualizing blood flow
Doppler effect
• Christian Andreas Doppler(1803-1853),austrian physicist & mathemetician formulated his theory in 1842
• Observed change in the frequency of transmitted waves when relative motion exists between the source of wave & an observer
• First medical applications of doppler sonography initiated during late 1950’s
• First pulsed-wave doppler equipment developed by Donald Baker,Dennis Watkins & John Reid worked on this project in 1966 produced one of first pulsed Doppler devices
Convex 3.5 MHzFor abdominal and OB/GYN studies
Micro-convex: 6.5MHzFor transvaginal andtransrectal studies
Ultrasoundmachine
Ultrasound examination
3D USG
Sound waves sent at different angles
Returning echoes processed by sophisticated computer resulting in three dimentional volume image of fetus’s surface
First developed by Olaf Von Ramm 1987 OBS - Timing of 3d scan between 26 to 30wks
4D USG
• Similar to 3D usg with the difference associated with time
4D allows 3 dimentional picture in real time
it is reffered to 4D when baby is moving in 3D
Elastography
Maps the elastic properties of soft tissueGives diagnostic information about disease by saying whether tissue is hard or softOffers very high contrast between masses and host tissuesThe acoustic radiation force moves the tissue and detect distorsion by speckle trackingResults are quantitativeFound applications in breast,liver prostate,thyroid
Ultrasound therapyRole in tissue ablation therapy in the form of high intensity focused
ultrasound
Exploits thermal effects of high power ultrasound beams focused on very small target tissue
Use frequency 0.7 to 3.3 mhz
More precise, easy to handle compared to radiotherapy
In ligament sprains,lithotripsy,cataract,acoustic targeted drug delivery,cancer therapy,thrombolysis etc
Computerized Tomography
Also known as computerized axial tomography[CAT]
Imaging of a cross sectional slice of the body using X-rays.
Invented by Dr. G. N. Housfield in 1971. Received the Nobel prize in medicine in 1979.
The method is constructing images from large number of measurements of x-ray transmission through the patient.
The resulting images are tomographic maps of the X-ray linear attenuation coefficient.
• Hounsfield built a prototype head scanner & tested it on a preserved human brain later on himself
• In 1971 CT scanning introduced into medical practice with a successful scan on cerebral cyst patient at Atkinson Morley’s hospital London
• In 1975 he built a whole body scanner
• In early experiments he used gamma source & it took 9 days to acquire image data & 2 ½ hrs to reconstruct image
• He replaced gamma source with x ray tube, scan time reduced to 9 hrs
ALLAN M.CORMACK
• 1979 – nobel prize shared with DR.Hounsfield developed solutions to mathematical problems in CT
• Principle - The density of the tissue passed by x ray beam can be measured from calculation of the attenuation coeffient
• Two processes of absorption photoelectric effect compton effect Measure transmission of thin beam of x rays through full
scan of body Image of that section taken from different angles,allows to
retrieve information on the depth Consists of square matrix of elements(pixel) & volume
element (voxel)
CT-First generation
• Single x ray source • Beam – pencil beam
• Detector rotate slightly
• Translate/rotate scanner
• Duration of time 25 to 30 mins
• Resolution very poor
Second generation
• Design – multiple detectors upto 30
• X rays beam – fan shaped
• Translate – rotate
• Duration of scan - <90 secs
Third generation
• Design – larger array of detectors
• 300-700 detectors ,circular
• Beam – fan shaped x ray beam
• Tube and detector arrays rotate around patient
• Rotate rotate scanner
• Duration of scan – 5sec
Fourth generation
• Detector – multiple >2000 arranged in outer ring fixed
• Beam – fan shaped
• Rotate – fixed scanner
• Duration of scan few seconds
Fifth generation
• X ray tube is a large ring that circles patient
• Use – cardiac tomography imaging “cine CT”
• Stationary/stationary geometry
Spiral/helical ct
• Design – x ray tube rotates as patient moved smoothly into x ray scan field
• Source rotation,table translation,data acquition
• Advantages
speed-30 sec for abdomen,chest improved detections improved contrast improved reconstruction improved 3D images
Seventh generation
• Design – multiple detector array• Turbo charged spiral• Upto 8 rows of detectors• Improvement in details• Cone beam and multiple parallel rows
of detectors• Reducing scan time,increase z
resolution• Very expensive
Attenuation coefficients of several tissues expressed
in Hounsfield units.
Magnetic Resonance Imaging (MRI)
1946 - NMR Discovered by two physicists Felix Bloch &Edward Mills Purcell
1952 - They received nobel prize in physics
1971 - Use of NMR to produce 2D images made by Paul Lauterbur 1976 - First clinical human MRI
2003 - Nobel prize for Lauterbur & Mansfield
Uses strong magnetic fields and radiowaves to form image of the body
Used for medical diagnosis,staging of disease,follow up without exposure to radiation
How it works
First – mri creates steady state of magnetism within human body by placing the body in a steady magnetic field
Second – mri stimulates body with radiowaves to change the steady state orientation of protons
Third – mri machine stops the radiowaves & register the body’s electromagnetic transmission
Fourth – transmitted signal used to construct internal images of body
MRI machine
Neuroimaging more sensitive for small tumors,CNS diseases guided stereotactic surgery radiosurgery(av malformations,tumors)
Cardiovascular MI,cardiomyopathies,CHD,ironoverload
Musculoskeletal spine imaging,joint disease,soft tissue tumors
Oncology,Liver,GI tract,functional MRI
Specialized applications
Diffusion MRI MR angiography
MR spectroscopy Functional MRI
Real time MRI Interventional MRI
MR guided focused ultrasound Multinuclear imaging Molecular imaging by MRI
• Advantage – ability to produce images in axial,coronal,saggital & multiple oblique planes
• Gives best soft tissue contrast of all imaging modalities
• CI – pacemakers,cochlear implants,aneurysm clips,metal fragments in eye
• Potential advancement – functional imaging,cardiovascular MRI,MRI guided therapy
Nuclear Imaging
PET
• Concept of emission and transmission tomography introduced by David E.Kuhl in late 1950s
• In 1961 James Robertson built the first single plane PET Scan,nick named “head-shrinker”
• Development of labeled 2FDG was a major factor in expanding in the scope of PET imaging
• The compound was first administered to two volunteers in aug 1976,at university of pennsylvania
•Modern non invasive imaging technique for quantification of radioactivity in vivo
•Involves use of radiopharmaceutical injected into body & its accumulation in body detected,quantified & interpreted
Concept• radiolabelled biocompound 2-fluoro-2-deoxy-D-glucose injected iv• uptake of compound followed by breakdown occurs in cells• tumors have high metabolic rate hence this compound metabolised by • tumor cells• FDG metabolised to FDG 6 phosphate • further not metabolised by tumor cells hence accumulates• accumulation is quantified
Whole body PET
Nuclear camera
Radionuclide (isotope) scan
• Radionuclide is a chemical which emits a type of radioactivity called gamma rays
• Tiny amount of radionuclide put into body• Cells which are more active will take up more of
radionuclide & emits more gamma rays• Detected by gamma camera,converted into
electrical signal & sent to computer• Computers builds into different colours/shades of
grey
SPECT (single photon emission computerized tomography)
• Tomographic slice is reconstructed from photons emitted by the radio isotope in a nuclear medicine study
• SPECT is 3D Tomographic technique that uses Gamma Camera data from many projections and reconstructed in different planes
SPECT Machine
THANK YOU